The Justice Department appears to be stepping up its antitrust probe of Google's settlement last year of a class-action lawsuit filed by groups representing authors and publishers, according to reports in The New York Times and The Wall Street Journal.

The Justice Department has sent formal requests for information, called civil investigative demands, or CIDs, to publishers involved in the settlement, according to the reports. The increased scrutiny may signal the Justice Department's opposition to the settlement, which still requires court approval.

Under the proposed $125 million settlement with the Authors Guild and the Association of American Publishers, announced in October, Google would have the right to show content from books online that are still in copyright but that are no longer in print. In addition, those copyright holders could be paid for online sales of their books.

Authors and publishers may opt out of the proposed settlement, but if they do nothing, they're considered part of it. That includes authors who can't be located.

Google is digitizing the works from many major libraries, including the New York Public Library and the libraries at Stanford and Harvard universities, and is making those texts searchable on pages with advertisements. The Authors Guild, which represents more than 8,000 authors, sued Google in September 2005, alleging that the company's digitizing initiative amounted to "massive" copyright infringement. Five large publishers filed a separate lawsuit as representatives of the Association of American Publishers.

Currently, users of Google Book Search are able to view snippets of books online. The settlement agreement would allow Google to make whole pages of copyright works available to online searchers.